INHERITANCE IN ASEXUAL REPRODUCTION 173 



number of tentacles of the original 20, the oral ends, was 7.05 ± 

 0.09. The mean number regenerated by the aboral ends was 

 6.42 ±0.09. The regenerated oral ends produced 146 buds, 

 the aboral ends, 132 buds within 28 days after the operation's. 

 The mean number of tentacles of the buds from the oral ends was 

 6.88 ±0.03; that of the buds from the aboral ends was 6.59 ±0.04; 

 the difference here is 0.29 ±0.004 in favor of the ofTspring of the 

 polyps which were required to carry out the lesser regenerative 

 processes. Clearly, the same factors which cause a reduction 

 in the number of tentacles in the parents (the call for an expendi- 

 ture of energy in regeneration) cause also a reduction in the 

 number of tentacles of their offspring. 



In order to test the length of time during which the after- 

 effects of injury to the parents influence the number of tentacles 

 of the buds, the mean number of tentacles of all first, all second, 

 etc., buds produced after regeneration by the oral and aboral 

 ends was computed. This is shown in figure 3. After the ninth 

 bud the graphs are based upon too small numbers to be sig- 

 nificant. It is clear from this figure that immediately after 

 regeneration the buds produced have few tentacles and that the 

 number of tentacles of successive buds increases rapidly until, 

 after five or six have been formed, the normal condition is 

 regained. 



These experiments show that certain environmental agents, 

 acting upon Hydra, tend to produce variation in a given direc- 

 tion in both parent and offspring, either, as in the first case, by 

 acting simultaneously upon both parent and bud, or, as in the 

 second case, by affecting the bud only indirectly through a 

 reduction in the vitality of the parent. Although only two such 

 agents have been studied experimentally it is probable that 

 many others have a like effect. Parke has shown that the 

 bacterial conditions leading to depression in his cultures brought 

 about a reduction in the number of tentacles of the polyps. I 

 have found that polyps which have just recovered from de- 

 pression tend to produce one or more very minute buds with 

 few tentacles. Polyps kept in water of high salt content become 

 small and dark-colored and produce small dark-colored buds. 



